6. ACRYLATE RESINS
A new development of widespread importance in the synthetic resin industry is the commercial production of the polymers of certain derivatives of acrylic acid. The commercial exploitation of the acrylates is another example of the belated realization of the value of substances known for many years. Acrylic acid has been known for about a hundred years, and the polymer of methyl acrylate was first described in 1880. It was not until 1927, however, that a suitable method for their commercial production was developed. The study of the many derivatives of acrylic and methacrylic acids leads to the conclusion that those of greatest practical application in the resin field are the lower esters, such as methyl and ethyl, polymerized separately or together.
Colorless transparency, stability against aging, thermoplasticity, and chemical resistance to many reagents are the general characteristics of the acrylate resins. In consistency they range from soft, sticky, semiliquids to hard, tough, thermoplastic solids. Since these widely varying properties are obtained by control of manufacturing conditions, rather than by the use of plasticizers, the resins retain their initial properties indefinitely. Aging and weathering have no effect as they are stable under exposure to heat, light, and oxidizing agents. The methacrylates are harder and tougher but less elastic than the acrylates.